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Behavior of Spinning Particles Near Wormholes

Examining how spin affects particle dynamics in traversable wormholes.

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Wormholes are fascinating objects in theoretical physics that connect two distant parts of space. They have captured the imagination of scientists and the public alike, often seen as potential shortcuts through the universe. This article looks at how spinning particles behave when moving around a specific type of wormhole known as the Morris-Thorne traversable wormhole.

The motion of particles near these wormholes can be described using certain equations that take into account both their movement and spin. Spin refers to the intrinsic angular momentum that particles possess, a property that plays an important role in the overall dynamics of these particles.

What Are Wormholes?

Wormholes can be thought of as bridges between two separate points in space. They allow for travel between these points without having to cover the distance in between. The Morris-Thorne wormhole is a well-studied example that is mathematically simple yet highly interesting. It is spherically symmetric, meaning it looks the same from all directions. The wormhole connects two regions of space, creating a "throat" through which a traveler can pass.

One key characteristic of such wormholes is that they do not have event horizons or singularities, which means they do not trap light or matter. In essence, they appear to be open passages through spacetime.

Spin Supplementary Conditions (SSCs)

When studying spinning particles near a wormhole, scientists use a set of equations called the Mathisson-Papapetrou-Dixon equations. These equations describe how particles move while accounting for their spin. However, to make the equations workable, scientists need to use something known as a Spin Supplementary Condition (SSC). An SSC helps to close the equations, providing a complete description of the motion.

Various SSCs can be used, and each choice can lead to different predictions about the motion of spinning particles. The most common ones include the Tulczyjew-Dixon, Mathisson-Pirani, and Ohashi-Kyrian-Semerák conditions. Each of these conditions gives a slightly different perspective on how the particles are positioned and how they behave while spinning.

Why Compare Different SSCs?

The choice of SSC is not just a mathematical convenience; it can significantly affect how we view the motion of particles in gravitational fields, especially around complicated structures like wormholes. By comparing the different SSCs, we can gain insights into their implications for particle dynamics.

This comparison can help scientists better understand the physical realities of wormholes and how spinning particles interact with them. Such insights could also contribute to broader discussions about gravitational theories and our understanding of the universe.

How Does Spin Affect Particle Dynamics?

In the case of spinning particles, their motion does not simply follow the standard paths defined by gravity. Instead, their spin introduces additional dynamics, affecting their trajectories and the forces they experience. When analyzing the motion of spinning particles around a wormhole, one must consider how their spin interacts with the gravitational field produced by the wormhole.

The influence of spin can be complex, leading to behaviors that differ from non-spinning (or test) particles. As the spin increases, the underlying physics may change, potentially allowing for new insights into gravitational interactions.

Key Components of the Study

Orbital Frequency

One of the primary aspects to examine is the orbital frequency, which is how fast a particle moves around the wormhole. This frequency is influenced by both the mass of the wormhole and the particle's spin. The equations used to derive the orbital frequency can be expanded to account for the effects of spin, revealing how the frequency changes at different orders of approximation.

In simpler terms, when you apply different SSCs, you might find that the orbital frequency changes depending on the reference point you choose. This understanding can influence our expectations about how fast particles can travel in such gravitational fields.

Innermost Stable Circular Orbit (ISCO)

Another important concept is the ISCO, which represents the smallest orbit in which a particle can remain stable without spiraling into the wormhole or flying away. The ISCO can change depending on the spin and the selected SSC. Analyzing how the ISCO varies with the different SSCs can yield valuable information about the stability of orbits near wormholes.

Understanding the ISCO is crucial, especially when considering astrophysical phenomena such as matter accumulating around a wormhole or the generation of gravitational waves resulting from particles moving in these regions.

The Orbital Parameters

In the analysis, two significant parameters are of particular interest: the orbital frequency and the ISCO radius. Both are influenced by the SSC chosen, and this study aims to quantify those differences.

Comparing SSCs

The study involves calculating the orbital frequencies using different SSCs. Each SSC leads to a polynomial equation describing the orbital frequency as a function of the particle's spin. The results indicate that at zero order, all SSCs yield the same frequency, corresponding to what one would expect for a non-spinning particle. However, as higher-order terms are included, discrepancies appear.

For instance, the first order remains equivalent across SSCs, but by the time the second order is considered, significant differences emerge, particularly with the OKS condition. This pattern continues, with all SSCs differing more noticeably as higher-order terms are considered.

ISCO Radius Analysis

The ISCO radius serves as a critical marker for assessing the gravitational influence around a wormhole. With the SSCs applied, it's found that the ISCO radius decreases as the particle's spin increases. This trend is consistent across all studied SSCs and wormhole configurations.

Notably, deviations occur at specific spin values-especially for the OKS SSC-where the ISCO radius diverges, indicating potential instability. Such divergence points may provide insights into the limits of stability for spinning particles in the vicinity of wormholes.

Corrections for Centroids

Each SSC references a unique "centroid" for the spinning particle, which can influence the calculated properties. To bring the results of the different SSCs closer together, corrections can be applied.

Radial Corrections

Radial corrections adjust the position of the centroid to improve alignment between different SSC predictions. Applying these corrections may enhance the convergence between the SSCs, facilitating a clearer comparison of results.

The radial correction leads to changes in both orbital frequency and ISCO radius. After applying these corrections, the predictions from the TD and MP SSCs tend to align more closely, suggesting that the radial position is a significant factor.

Spin Corrections

In addition to correcting the centroid's position, modifications to the spin values can also be made. These spin corrections help standardize the comparisons across the different SSCs.

These corrections can markedly influence the ISCO parameters, allowing for more accurate comparisons between the behaviors predicted by each SSC. By applying both radial and spin corrections, researchers can gain deeper insights into how the parameters of a spinning particle interact with the geometry of the wormhole.

Conclusion

The study of spinning particles around traversable wormholes using different SSCs reveals fascinating dynamics. The behavior of particles, particularly in terms of their orbital frequency and ISCO radius, can vary significantly depending on the chosen SSC.

Through careful comparison and the application of centroid and spin corrections, researchers can better understand the underlying physics of wormholes and their implications for both theoretical studies and potential applications in astrophysics.

By continuing to explore these dynamics, scientists may find new ways to understand the universe's structure and the intricate relationship between spin, gravity, and the fabric of spacetime.

Original Source

Title: Comparing spin supplementary conditions for particle motion around traversable wormholes

Abstract: The Mathisson-Papapetrou-Dixon (MPD) equations describe the motion of spinning test particles. It is well-known that these equations, which couple the Riemann curvature tensor with the antisymmetric spin tensor S, together with the normalization condition for the four-velocity, is a system of eleven equations relating fourteen unknowns. To ``close'' the system, it is necessary to introduce a constraint of the form V_\mu S^{\mu \nu} = 0, usually known as the spin supplementary condition (SSC), where V_\mu is a future-oriented reference vector satisfying the normalization condition V_\alpha V^\alpha = -1. There are several SSCs in the literature. In particular, the Tulzcyjew-Dixon, Mathisson-Pirani, and Ohashi-Kyrian-Semer\'ak are the most used by the community. From the physical point of view, choosing a different SSC (a different reference vector $V^\mu$) is equivalent to fixing the centroid of the test particle. In this manuscript, we compare different SSCs for spinning test particles moving around a Morris-Thorne traversable wormhole. To do so, we first obtain the orbital frequency and expand it up to third-order in the particle's spin; as expected, the zero-order coincides with the Keplerian frequency, the same in all SSCs; nevertheless, we found that differences appear in the second order of the expansion, similar to the Schwarzschild and Kerr black holes. We also compare the behavior of the innermost stable circular orbit (ISCO). Since each SSC is associated with a different centroid of the test particle, we analyze (separately) the radial and spin corrections for each SSC. We found that the radial corrections improve the convergence, especially between Tulzcyjew-Dixon and Mathisson-Pirani SSCs. In the case of Ohashi-Kyrian-Semer\'ak, we found that the spin corrections remove the divergence for the ISCO and extend its existence for higher values of the particle's spin.

Authors: Carlos A. Benavides-Gallego, Jose Miguel Ladino, Eduard Larrañaga

Last Update: 2023-06-30 00:00:00

Language: English

Source URL: https://arxiv.org/abs/2306.17394

Source PDF: https://arxiv.org/pdf/2306.17394

Licence: https://creativecommons.org/licenses/by/4.0/

Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.

Thank you to arxiv for use of its open access interoperability.

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